fix(market): search your zone by a coarse prefix, not the exact cell

Discovery searched the full 5-char geohash (~2.4 km) with an exact Nostr tag
match, so two devices in adjacent cells never found each other even though
publish emits the full NIP-52 prefix ladder. Search now coarsens the area to a
configurable precision (SocialSettings.searchPrecision, default 4 ~20 km) via
searchPrefix(), with a human-worded 'how far' selector (Very close / Around
here / My region -> 5/4/3) in the market setup sheet.

Also: surface a clear 'couldn't reach the servers' message when no relay
accepts a share (instead of 'shared 0'), and add wss://relay.comunes.org as the
first default relay (reliable community home; public relays are backup).

Tests: settings precision (default/clamp/roundtrip), searchPrefix helper,
neighbour-cell discovery regression (offers_cubit + commons_core nostr
transports), and the range-selector widget test.

apps/app_seeds/lib/i18n/ast.i18n.json

@@ -370,7 +370,12 @@
     "nothingToShare": "Marca primero dalguna simiente pa regalar, trocar o vender",
     "useLocation": "Usar el mio allugamientu averáu",
     "locationFailed": "Nun se pudo consiguir el to allugamientu — comprueba que l'allugamientu ta activáu y el permisu concedíu",
-    "queued": "Guardáu — compartirémosles cuando tengas conexón"
+    "queued": "Guardáu — compartirémosles cuando tengas conexón",
+    "shareFailed": "Nun se pudo coneutar colos sirvidores — les tos granes nun se compartieron. Vuelvi a intentalo nun momentu.",
+    "rangeLabel": "Hasta ónde guetar",
+    "rangeNear": "Bien cerca",
+    "rangeArea": "Pela mio zona",
+    "rangeRegion": "La mio rexón"
   },
   "profile": {
     "title": "El to perfil",